This invention relates to a waveguide slot antenna and a method of manufacturing thereof. More particularly, the invention relates to a waveguide slot antenna designed as a multi-layer structure in the form of waveguide slot with the characteristics of a sharp directivity and high gain. Also, the invention relates to an antenna manufacturing method that provides a conductive characteristic to dielectric synthetic resin by thinly coating the synthetic resin with a conductive metal after injection molding.
In general, a cross section of waveguides has many different shapes. According to the shape of a waveguide, it is classified as a circular waveguide, rectangular waveguide, and elliptical waveguide. A waveguide is a kind of a metal pipe that acts as a high frequency pass filter. The guide mode has a fixed cut off wavelength. This basic mode is determined by the length of a waveguide. The waveguide is a type of a transmission line for transmitting a high frequency electronic wave above the microwave level. The waveguide is made of a conductive substance such as copper and an electromagnetic wave can be transmitted through the guide. The waveguide acts as a high frequency filter in order to allow the transmission of a wavelength range below the cut off wavelength.
The wavelength of a wave which travels along the axis of a waveguide is called a guide wavelength. This guide wavelength is longer than an exciter wavelength. The transmission line for low frequency is usually a pair of copper lines. For high frequency, there are increasingly more conductive loss due to surface effect and dielectric loss due to the surrounding dielectric bodies. However, for the transmission of electromagnetic wave through a waveguide, there is a small amount of loss due to the reflection from the guide walls inside of the waveguide.
The basic mode of a waveguide as mentioned above is determined by its size. The above waveguide has a small amount of damping compared to a parallel 2 line type or coaxial cable and therefore, it can be used for a microwave transmission line for a high power output purpose.
A micro strip patch array antenna using a dielectric substrate has now been commercialized after the development of a dielectric material that results a little loss even in high frequency.
However, the dielectric loss is inevitable due to the characteristics of the dielectric substrate. Also, there are many difficulties involved in the manufacturing of a high gain antenna due to the resistance loss of a conductor and the high cost of dielectric substrates impose a limitation to commercialization.
A waveguide slot antenna which does not utilize a dielectric substance but has a number of holes in the shape of a slot. The history of the waveguide slot antenna goes back much further than a flat antenna but due to the difficulties involving its weight, size and precision for manufacturing, the flat antenna made of a dielectric substance is in much wider use.
Especially, it is much more difficult to design a waveguide slot antenna than a flat antenna made of a dielectric substance. It is more likely to show the Grating Rove characteristic and a high gain antenna is very hard to manufacture.